util/qemu-thread-posix.c: Replace OS ifdefs with CONFIG_HAVE_SEM_TIMEDWAIT

Message ID 1504613972-15847-1-git-send-email-peter.maydell@linaro.org
State Superseded
Headers show
Series
  • util/qemu-thread-posix.c: Replace OS ifdefs with CONFIG_HAVE_SEM_TIMEDWAIT
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Commit Message

Peter Maydell Sept. 5, 2017, 12:19 p.m.
In qemu-thread-posix.c we have two implementations of the
various qemu_sem_* functions, one of which uses native POSIX
sem_* and the other of which emulates them with pthread conditions.
This is necessary because not all our host OSes support
sem_timedwait().

Instead of a hard-coded list of OSes which don't implement
sem_timedwait(), which gets out of date, make configure
test for the presence of the function and set a new
CONFIG_HAVE_SEM_TIMEDWAIT appropriately.

In particular, newer NetBSDs have sem_timedwait(), so this
commit will switch them over to using it. OSX still does
not have an implementation.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

---
It would be nice to gradually reduce the number of places
we do per-OS ifdeffery in favour of checking for the specific
feature we care about in each case...
Tested on Linux, NetBSD, OSX.

 configure                   | 15 +++++++++++++++
 include/qemu/thread-posix.h |  2 +-
 util/qemu-thread-posix.c    | 10 +++++-----
 3 files changed, 21 insertions(+), 6 deletions(-)

-- 
2.7.4

Comments

Kamil Rytarowski Sept. 5, 2017, 12:57 p.m. | #1
On 05.09.2017 14:19, Peter Maydell wrote:
> In qemu-thread-posix.c we have two implementations of the

> various qemu_sem_* functions, one of which uses native POSIX

> sem_* and the other of which emulates them with pthread conditions.

> This is necessary because not all our host OSes support

> sem_timedwait().

> 

> Instead of a hard-coded list of OSes which don't implement

> sem_timedwait(), which gets out of date, make configure

> test for the presence of the function and set a new

> CONFIG_HAVE_SEM_TIMEDWAIT appropriately.

> 

> In particular, newer NetBSDs have sem_timedwait(), so this

> commit will switch them over to using it. OSX still does

> not have an implementation.

> 


The NetBSD part looks fine. It builds fine on NetBSD/amd64 8.99.2. All
tests pass (with disabled PaX MPROTECT).

> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>


Reviewed-by: Kamil Rytarowski <n54@gmx.com>


> ---

> It would be nice to gradually reduce the number of places

> we do per-OS ifdeffery in favour of checking for the specific

> feature we care about in each case...

> Tested on Linux, NetBSD, OSX.

> 

>  configure                   | 15 +++++++++++++++

>  include/qemu/thread-posix.h |  2 +-

>  util/qemu-thread-posix.c    | 10 +++++-----

>  3 files changed, 21 insertions(+), 6 deletions(-)

> 

> diff --git a/configure b/configure

> index fb7e34a..aa8d4d9 100755

> --- a/configure

> +++ b/configure

> @@ -4448,6 +4448,18 @@ if compile_prog "" "" ; then

>  fi

>  

>  ##########################################

> +# check if we have sem_timedwait

> +

> +sem_timedwait=no

> +cat > $TMPC << EOF

> +#include <semaphore.h>

> +int main(void) { return sem_timedwait(0, 0); }

> +EOF

> +if compile_prog "" "" ; then

> +    sem_timedwait=yes

> +fi

> +

> +##########################################

>  # check if trace backend exists

>  

>  $python "$source_path/scripts/tracetool.py" "--backends=$trace_backends" --check-backends  > /dev/null 2> /dev/null

> @@ -5680,6 +5692,9 @@ fi

>  if test "$inotify1" = "yes" ; then

>    echo "CONFIG_INOTIFY1=y" >> $config_host_mak

>  fi

> +if test "$sem_timedwait" = "yes" ; then

> +  echo "CONFIG_SEM_TIMEDWAIT=y" >> $config_host_mak

> +fi

>  if test "$byteswap_h" = "yes" ; then

>    echo "CONFIG_BYTESWAP_H=y" >> $config_host_mak

>  fi

> diff --git a/include/qemu/thread-posix.h b/include/qemu/thread-posix.h

> index e5e3a0f..f4296d3 100644

> --- a/include/qemu/thread-posix.h

> +++ b/include/qemu/thread-posix.h

> @@ -21,7 +21,7 @@ struct QemuCond {

>  };

>  

>  struct QemuSemaphore {

> -#if defined(__APPLE__) || defined(__NetBSD__)

> +#ifndef CONFIG_SEM_TIMEDWAIT

>      pthread_mutex_t lock;

>      pthread_cond_t cond;

>      unsigned int count;

> diff --git a/util/qemu-thread-posix.c b/util/qemu-thread-posix.c

> index 4e95d27..7306475 100644

> --- a/util/qemu-thread-posix.c

> +++ b/util/qemu-thread-posix.c

> @@ -168,7 +168,7 @@ void qemu_sem_init(QemuSemaphore *sem, int init)

>  {

>      int rc;

>  

> -#if defined(__APPLE__) || defined(__NetBSD__)

> +#ifndef CONFIG_SEM_TIMEDWAIT

>      rc = pthread_mutex_init(&sem->lock, NULL);

>      if (rc != 0) {

>          error_exit(rc, __func__);

> @@ -196,7 +196,7 @@ void qemu_sem_destroy(QemuSemaphore *sem)

>  

>      assert(sem->initialized);

>      sem->initialized = false;

> -#if defined(__APPLE__) || defined(__NetBSD__)

> +#ifndef CONFIG_SEM_TIMEDWAIT

>      rc = pthread_cond_destroy(&sem->cond);

>      if (rc < 0) {

>          error_exit(rc, __func__);

> @@ -218,7 +218,7 @@ void qemu_sem_post(QemuSemaphore *sem)

>      int rc;

>  

>      assert(sem->initialized);

> -#if defined(__APPLE__) || defined(__NetBSD__)

> +#ifndef CONFIG_SEM_TIMEDWAIT

>      pthread_mutex_lock(&sem->lock);

>      if (sem->count == UINT_MAX) {

>          rc = EINVAL;

> @@ -256,7 +256,7 @@ int qemu_sem_timedwait(QemuSemaphore *sem, int ms)

>      struct timespec ts;

>  

>      assert(sem->initialized);

> -#if defined(__APPLE__) || defined(__NetBSD__)

> +#ifndef CONFIG_SEM_TIMEDWAIT

>      rc = 0;

>      compute_abs_deadline(&ts, ms);

>      pthread_mutex_lock(&sem->lock);

> @@ -304,7 +304,7 @@ void qemu_sem_wait(QemuSemaphore *sem)

>      int rc;

>  

>      assert(sem->initialized);

> -#if defined(__APPLE__) || defined(__NetBSD__)

> +#ifndef CONFIG_SEM_TIMEDWAIT

>      pthread_mutex_lock(&sem->lock);

>      while (sem->count == 0) {

>          rc = pthread_cond_wait(&sem->cond, &sem->lock);

>
Eric Blake Sept. 5, 2017, 2:11 p.m. | #2
On 09/05/2017 07:19 AM, Peter Maydell wrote:
> In qemu-thread-posix.c we have two implementations of the

> various qemu_sem_* functions, one of which uses native POSIX

> sem_* and the other of which emulates them with pthread conditions.

> This is necessary because not all our host OSes support

> sem_timedwait().

> 

> Instead of a hard-coded list of OSes which don't implement

> sem_timedwait(), which gets out of date, make configure

> test for the presence of the function and set a new

> CONFIG_HAVE_SEM_TIMEDWAIT appropriately.

> 

> In particular, newer NetBSDs have sem_timedwait(), so this

> commit will switch them over to using it. OSX still does

> not have an implementation.

> 

> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

> ---

> It would be nice to gradually reduce the number of places

> we do per-OS ifdeffery in favour of checking for the specific

> feature we care about in each case...


Yes, that's always been autoconf's philosophy: feature tests trump
platform tests every time, because platforms can add features over time,
and because an ifdef on a single feature test is easier to read than a
list of platform names.

> Tested on Linux, NetBSD, OSX.

> 


Reviewed-by: Eric Blake <eblake@redhat.com>


-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org

Patch

diff --git a/configure b/configure
index fb7e34a..aa8d4d9 100755
--- a/configure
+++ b/configure
@@ -4448,6 +4448,18 @@  if compile_prog "" "" ; then
 fi
 
 ##########################################
+# check if we have sem_timedwait
+
+sem_timedwait=no
+cat > $TMPC << EOF
+#include <semaphore.h>
+int main(void) { return sem_timedwait(0, 0); }
+EOF
+if compile_prog "" "" ; then
+    sem_timedwait=yes
+fi
+
+##########################################
 # check if trace backend exists
 
 $python "$source_path/scripts/tracetool.py" "--backends=$trace_backends" --check-backends  > /dev/null 2> /dev/null
@@ -5680,6 +5692,9 @@  fi
 if test "$inotify1" = "yes" ; then
   echo "CONFIG_INOTIFY1=y" >> $config_host_mak
 fi
+if test "$sem_timedwait" = "yes" ; then
+  echo "CONFIG_SEM_TIMEDWAIT=y" >> $config_host_mak
+fi
 if test "$byteswap_h" = "yes" ; then
   echo "CONFIG_BYTESWAP_H=y" >> $config_host_mak
 fi
diff --git a/include/qemu/thread-posix.h b/include/qemu/thread-posix.h
index e5e3a0f..f4296d3 100644
--- a/include/qemu/thread-posix.h
+++ b/include/qemu/thread-posix.h
@@ -21,7 +21,7 @@  struct QemuCond {
 };
 
 struct QemuSemaphore {
-#if defined(__APPLE__) || defined(__NetBSD__)
+#ifndef CONFIG_SEM_TIMEDWAIT
     pthread_mutex_t lock;
     pthread_cond_t cond;
     unsigned int count;
diff --git a/util/qemu-thread-posix.c b/util/qemu-thread-posix.c
index 4e95d27..7306475 100644
--- a/util/qemu-thread-posix.c
+++ b/util/qemu-thread-posix.c
@@ -168,7 +168,7 @@  void qemu_sem_init(QemuSemaphore *sem, int init)
 {
     int rc;
 
-#if defined(__APPLE__) || defined(__NetBSD__)
+#ifndef CONFIG_SEM_TIMEDWAIT
     rc = pthread_mutex_init(&sem->lock, NULL);
     if (rc != 0) {
         error_exit(rc, __func__);
@@ -196,7 +196,7 @@  void qemu_sem_destroy(QemuSemaphore *sem)
 
     assert(sem->initialized);
     sem->initialized = false;
-#if defined(__APPLE__) || defined(__NetBSD__)
+#ifndef CONFIG_SEM_TIMEDWAIT
     rc = pthread_cond_destroy(&sem->cond);
     if (rc < 0) {
         error_exit(rc, __func__);
@@ -218,7 +218,7 @@  void qemu_sem_post(QemuSemaphore *sem)
     int rc;
 
     assert(sem->initialized);
-#if defined(__APPLE__) || defined(__NetBSD__)
+#ifndef CONFIG_SEM_TIMEDWAIT
     pthread_mutex_lock(&sem->lock);
     if (sem->count == UINT_MAX) {
         rc = EINVAL;
@@ -256,7 +256,7 @@  int qemu_sem_timedwait(QemuSemaphore *sem, int ms)
     struct timespec ts;
 
     assert(sem->initialized);
-#if defined(__APPLE__) || defined(__NetBSD__)
+#ifndef CONFIG_SEM_TIMEDWAIT
     rc = 0;
     compute_abs_deadline(&ts, ms);
     pthread_mutex_lock(&sem->lock);
@@ -304,7 +304,7 @@  void qemu_sem_wait(QemuSemaphore *sem)
     int rc;
 
     assert(sem->initialized);
-#if defined(__APPLE__) || defined(__NetBSD__)
+#ifndef CONFIG_SEM_TIMEDWAIT
     pthread_mutex_lock(&sem->lock);
     while (sem->count == 0) {
         rc = pthread_cond_wait(&sem->cond, &sem->lock);